1. Field of the Invention
The present invention relates to a powder particle jumping recording apparatus for forming an image by attaching a developer in powder particle form directly on a recording material without forming any electrostatic latent image.
2. Description of the Related Art
Conventionally what is called the electrophotographic recording apparatus has been widely used for the duplicator, facsimile, printer or the like. In the electrophotography invented in 1938 by P. F. Carlson, an electrostatic latent image is formed on a photoconductive light-sensitive material, and a toner constituting a charged powdery developer is adsorbed on it. Then the toner is transferred to a recording material to form an image, and fused by being heated for recording. With this electrophotography, the light-sensitive material used for forming an electrostatic latent image is expensive, and the maintenance cost is high. In recent years, the powder particle jumping recording technique has been proposed in Japanese Unexamined Patent Publication of an international application, JP-A 1-503221 (1989) and in a publication entitled "Forming Image by Powder Particle Flying Recording System and Evaluation" (first report), Image Electronics Society Journals Vol.22, No.3, 1993, pp.255-262.
FIG. 7 shows a principle of the powder particle jumping recording process based on FIG. 2 shown on page 255 of the above-mentioned publication. A developing roller 1 magnetically attracts toner 2 having a magnetic surface and conveys it to a recording section. In the recording section, a control electrode 3, a recording paper 4 and a back electrode 5 are arranged to be spaced from the surface of the developing roller 1. Upon application of a voltage to the control electrode 3 in such a manner as to attract the toner 2, the toner 2 is attracted by the Coulomb force based on the electric field generated from the control electrode 3 larger than the magnetic attraction exerted on the developing roller 1, and the toner jumps from the surface of the developing roller 1. The back electrode 5 is impressed with a high DC potential and accelerates the jumping toner 2. In the control electrode 3 are formed through holes through which the toner 2 is allowed to pass. The toner 2 thus accelerated is attached on the recording paper 4 inserted between the control electrode 3 and the back electrode 5 to form an image.
The prior art relating to a powder particle jumping recording apparatus are disclosed also in Japanese Unexamined Patent Publication JP-A 3-168770 (1991) and Japanese Unexamined Patent Publication of an internatioal application, JP-A 4-505899 (1992). The apparatus disclosed in JP-A 3-168770 has such a configuration that a toner carrier corresponding to the developing roller and toner passage means corresponding to the control electrode are integrated with each other as a single unit removable from the back electrode. JP-A 4-505899, on the other hand, discloses a technique in which the extraneous toner attached on the surface of the control electrode is cleaned off by a magnet contained in the developing roller.
In the prior arts described above, the back electrode assumes a tabular or a similar shape, and therefore the accelerated toner is liable to be scattered over a wide range. The scattering tendency of the toner often causes the toner to attach on the control electrode. JP-A 4-505899 discloses a configuration for cleaning the toner off from the control electrode by the magnetic force on the developing roller. In the case where a recording material is not loaded between the control electrode and the back electrode, however, the toner is liable to transfer to the back electrode, and any configuration is not disclosed for cleaning the toner that has transferred to the back electrode.